1. Field of the Invention
The present invention relates generally to electronic circuits and, more specifically, to data transmissions between two devices over a single-wire connection. The present invention more specifically applies to systems implementing protocols known as single-wire protocols (SWP).
2. Discussion of the Related Art
Single-wire communication protocols are defined between a master device and a slave device sharing a single-wire connection to transmit data to each other in simultaneous bidirectional fashion (full duplex). Most often, the signal transmitted by the master device to the slave device further is a clock signal enabling synchronizing the exchanges. In the master-device-to-slave-device direction, the duty cycle of a periodic signal is modulated according to the binary state to be transmitted. In the slave-device-to-master-device direction, the slave device modulates the charge that it exhibits on the connection according to the binary states of the data that it transmits. The detection by the slave device occurs by measurement of the duty cycle. The detection by the master device occurs by comparing to a threshold the level of the current pulled by the slave device from the connection. The charge modulation by the slave device generally occurs at the rate of the periodic signal, by positioning of the charge during low states, so that the charge to be detected by the master device is present all along the high state of the signal.
Document U.S. Pat. No. 5,903,607 describes an example of a data coding and transmission between a master circuit and a slave circuit.
The communication rate in a single-wire protocol is linked, among others, to the delay necessary for the detection on the master device side. It needs to be awaited for the levels to settle, after the rising edges of the signal, to perform the comparison.
Further, a detection by level is sensitive to the line noise, which imposes a relatively large security margin to differentiate the levels.